Human Placental estradiol 17 beta-dehydrogenase has been purified and crystallized. Efforts are centered on sequencing the enzyme and growing crystals large enough for X-ray diffraction studies to validate the affinity-labeling results as to which residues proximate which regions of the steroid as it binds at the active site. Affinity labeling studies of the structure of the steroid binding site of calf uterine estradiol receptor will be carried out. Efforts to purify, to homogeniety, estradiol 17 beta-dehydrogenase and estradiol 17 alpha-dehydrogenase for structural studies with affinity-labeling steroids are to get underway during this upcoming year.